Electric power-supply system



c. e. ADSIT ET AL 1,777,952

ELECTRIC POWER SUPPLY SYSTEM 2 Sheets-Sheet 1 Filed May 12, 1927 CD CD INVENTORS CHARLES G. ADSIT CHARLES E.BENNETT {y iirez'i' aii'arvzfya 0a. 7, 1930. c. G. ADSIT ETAL- 1,777,952

ELECTRIC POWER SUPPLY SYSTEM Filed May 12, 1927 2 Speets-Sheet 2 4 7 I o o i 7 l l Svwemtozs C'H/PRLES 6.40517 CHFIFL 5 E. BE/viva T1 AM M Patented a. 7, 1930 uni'rsnfsra' 'rns" oi mnnEsegAnsrr, or ANnE ws- DRIVE, AND cHAELEs E. ENNErnbE nEoA'rUE, 1

' GEORGIA PATENT OFFICE LELECTBQIC ,rowEn-su-rrrr sYs'r M App1ication gfile'd May 12,,

Our. invention relates itojelec-tric [power supply systems, andiparticularly to a direct current supply systeni for electric railways.

Among-the objects of ourinyentionrnay befmentioned .,(1:)" To provide a sectionalized or Zoned electriclrailway current supply system to which existing installations may be 0on yeniently andv adyantageously' converted (2), To pro ide afsectional or 'zoned trolley wire system, in. which each trolleywire. section or zone has 1tsseparate' feeder, so that trouble on one'section or Zone 111 not 1nter- ,fere with the power supply toor operation To provideja ower supply; systein of I of other sections or zones;

V the track return type, in which the current i densi y of. the track circuit is reducedtol a "minimum;

1(4); To eliminate. or iminimize injury-to rails, mtne'pi es, gasmains, heating rnains, power cables, telephone cables, bridges, and otherstructures, J a

(5:) To ininirnize the flow of currentin the track by; maintaining asubst'antial balance between the power feeders'of opposite polar unit; and

(6) T'o leliminate current losses in both the feederand ground return conductors;

To provide appropriate power station equipment and layout I for the effective operationfilf thesystemlj Various other advantages ;will be here inafter explained for will be clear to; those skilled the art, from the, accompanying draw ngsqlnWh1ch= T. Fig.-: 1 's ;a diagram;illustrating certain featuresoflourinvention; i j 3 f 2 is a diagram illustrating-a power s tron layout;.v H t 3=is a diagram of modified balancing 'Fig. 4 is a diagrani of a panel controlunit.

Referring 'to the diagram of 1, we

Qhaye Qindicated 15 a .trolley'gtrack upon whichrun, cars 16*proyided with thensual 1D: C., ,1notors whichtake their current "from ,ithe oye'rl'aid.trolley' wirelli'. The trolley ins-1m 1 3 6 iyitled finto sections 1 or Zones, a, epar'a'ted by SBCtlOHlIlSLllflilOIS .18..

1927., Serial 110,190,866.

The currentsupply to the trolley wire may be 'derivedirom a pair of generators 19 and 20 arranged in series thegener'ator 19 ,ha'vley wirel'l' means of feeder leads 27. H

Thus sections or zones at and c, Fig. 1, are

connected to the positive feeder 22, while sections or zones 6 andcl of thetrolley wire are connected to the teeder '21 of negative polarity. "The current flowing from the various sections orzones of the trolley Wire through the motors of the several cars 16, enters the track 15, and the latter is connected' through lead 23 to a neutral point intermediate the generators l9fand20, that is to say, to a point in: the series connection between the generators. f l

While the current supply'may be from generators 19, 20, e prefer to use these two machines as a balancing means to supply only a balancing current to keep the system in balance. WVhen these generators are used as balancers the main source of current supplied to feeders 21, 22 may come from are rectifiers25 (see Fig. 2) or other well known sources of current such as are commonly used in h gh power nstallat ons.

The drawlng 111 F gure the same feeder and are therefore of thesaine polarity. We point this out w th particular ity since it is ofpractical importance. from v 1 illustrates the w fact that where there are two or more parallel tracks, their trolley wires are sectionalized alike, and parallel sections are connected to the standpoint of-installation expense. Only standard insulation from supports is required, 1

Slnce the same source of power energlzes both POSltlVQ and negatlve feeders, and their respective trolley wire zones, the ground or track circuit is neutral to the source of power. ,The ground current in; the track instead of flowing back to the source of power, as has heretofore been the practice, now flows onlybetween' cars on the same track in adjacent zones. This path is comparatively Tia ' the track Will be only half what the same resistance.

:load would require in the usual feeding system, in which the entire feeder potential is returned to the-generator through the track 15'.

This obviously results in a far lower power loss inthe feeder, since as s well understood, current loss in transmission systemsv follows the law of the current squared times density of-current in the track circuit, and a great reduction in the length ofthe path of the current in the ground circuit, since the current does not return to the sourceo'f supply throughthe track. Inasmuch as the rail or groundcircuit is vof steel .or'iron, which is a metal of relatively high resistance, thereduction ofcurrent densityin this portion of the circuit,or the re'strictionoi the lengthof the, current path therethrough, greatly re duc'es' the curient loss in this side of the cir cuit.

lVIoreove'r the i is greatly reduced, due to the fact that the drop in potential in'the railicircuit is reduced to a minimum. This results'in-the practical elimination ofele'ctrolysis, since the current flow from the rails to'other structures, and the current flow fromsuch structures back to the rails, is so reduced (in fact practica1ly eliminated) that the cause of electrolysis reduced'to a minimum. There s also a re versal of polarity, since the flow of current in r dependent upon the movement of'cars'on adjacentzones, and'the d stance betweenthem.

This also serves to reduce electrolysis.

The resistance offered by the track circuit, a

as above mentioned, is due to the relatively high resistance of the track metal, tothe're sistan'ce of the track bondsyan d to thelength or" the current path. This resistance causes a high loss when the current-density is great,

as it now commonly is, by reason of the flow of the entire ground current througlrthe tracks'backto the source'of power; Thisloss' is also proportionalto the currentsquared times the resistance of the c rcuit. Conseqi'ie'ntly vWhere the current density is great,

the resistance loss is very high. On tie cone trary, inac'ciordance with the present invention, the average current density in the rail circuit times the average length of its path, is only asmajll traction of that now common in the usualtrack return circuit. If the current in the track circuit is reduced, for example to 1 0% of its normal value, then by reason the fact that the losses are proportioned to the current squared, the current loss in accord,-

ance with'the present system only l/ of theloss experienced in the systems now in common use.

The resultfis very much lower 7 difference of potential be tween the rails and other grounded structures 7 Again, drop of voltage nia conductor is' proportional to the resistance of the conductor, times the current value. Therefore, if

the average track circuit is only 1/10 of its normal value, the voltage drop in this portion of thecircuitis only 1/10" as'gr'eat; V V This great reductlon of current value and voltage drop in the track circuit reduces the e l eeqfe rlt er i l he see e e' t 01: other paths, and these paths are only for. the

comparatively short length of track through Whichitheocurrent'flows.

The'sectionalizingofthe trolley wire indiiierenceabove ground as in the usual sys I tern. No additional insulation is. required'on span wires or other supportsthan isus ually employed. 'The only additions fto the usual system are the sectioninsulators orbreaks installed in the trolley wires over which'the trolley wheel or collector passes, thus requir ing little cost for change'to' ;tl1e present'system; vN0 change whatsoever is required in the track circuit. f I a V 7 The power apparatus at the source'of power supply determines the potential difierencebetween the trolley wire and rail, and 7 maintams 1t constant by" reason of the neutral round connection. -Where 600 volts are required between the trolley and" ground or; V i

track, the power is transmitted at. 1200' volts;

while. at the'same. time maintaining 600 "volts I 7 betweenthe trolley and track of a the. rails is notaljway's in the same dlrection, .7

Breaks-in thecontinuity or thegr ioo section; circuit,

due to faulty bonding, become of less import the system'as a'whole. The reversal of current fiOW'WllQllf tllG car crosses from one zone to oanotherfdoesnot reverse the motorsor other devices onthe cars, since the reversal of.

pola -ay causes no reversal of direction" of the motor. Consequently carequipment may-be.

standard.

v In Fig. 2 we lia ve'indicated diagrammati- J cally an appropriatestation-layout, although this is subject to wide variation." -The power supplied to the feeders'2l and-'22'is derived from are rectifiers 25. Thi.sf current .is suiiicienttotake care of the lineload. Theb'aL ancing current supplied to the feeders 21am 7 22 is derived from the generators 19-an'd12'0,

to which alone the track circuit 15 is n,

nected at a point intermediate these series connected generators. Anyunbalanced con-- V diti'on in the feeders is taken "c'are of by'the operationof thesel'generators, th "operation 3 of which tends to rabrtiuit b ce. 7 5

Will" b notedpthe current e iesfield or generator I 20, .lis derive d from generator 19,17, 1

and vice area. f

J It will be apparentato those skilled. in the art that the generators19,20willoperate as I to "a motor-generator set. .The rotorso-f these generators are coupled together as shown at 24, Depending onwhether thereisla posiQ- "me or negative current in balancing connection'23, either machine 19 or willact as a 7 motor and drive the other machine as a generator to deliver the balancing current to, re; system "as mentioned;

store. balance in the above. 7 g c ;Assuming. that the system 1s connected. as

7 shown in*Fig. 1 and-with the generators 19-.

c and 20-used as balancers and the mainsource of currentYderived.from some means,: as is shown in Figure 2; then the, main current. which drives the motors in the cars 16 will be deliveredtothe bus bars2l, 22 or 210,220 froinvthe source andwilligo out from the;

bus bars through the" positive feeders to the trolleyjwire zones from thence'itwillgo down through the cars to'the track then through} V the track to the adjacent zones of oppositepolarity andtup through-the. cars in those zones'tothe trolley line and'negative feeder and backto the source'25. The only current that will pass through'the-tracks to the con ductor 28 will be balancing current supplied by the generators 19 and 20 tocounter'balance. any extra demand onthe posit ve or negativefeeder.

It'has been found practice-that under normal Conditions thefsystem is in. substantialorpractical balance 'andtherefore prac- .tically no current run's'through theconduc-f tor i23. f On that account 7 the ba'lan'cing. connection to track need not necessarilybe closed track to some place within oneor the otherf -of'the generators,- in the normal operatlon of these zones mayberev'ersed. Thus a continuous unbalanced condltion need not long prevail in our system since-1t 1s so easy to correct.

such condition. a

a but may be open undernormal-conditions, any mild unbalancedconditionbeing taken carefof automatically bythe normal operation of the generators or inotherwords such condition will vbe takenucareflof by an auto,-

matic shifting of the neutral point from the the ordinary type of gene rators. Because tween the bus bars 22; 21 and thefeeders'fto r 5 In Fig. 3' we have indicated, a modilied layout in which the-"seri s-fifi f leach ge e atoris subject to an automati'c relay control.

7 Various other balanced pbweii ,l iy ll ,@151

art;

rangements will occur to those skilled iin the In Fig. 1 wehave shown diagr ammatical ly the connections for changing the polarity of the feeders at will, while in Fig. 4 we have pictured, diagrammatically, a. station layout] wherein bus bars 210 and 220 correspond to feeders21 and 22. M i c a A distributing panel is associated with the bus bars, a panel unit 26 being provided for eachsection of the trolley wire and the .con-

nection tothe panel unit 26 being established through a lead 27 from the unit'to the appropriatetrolley wire section. Preferably the panel unit comprises a double throw switch 28 adapted to make connection with either'the positive terminal 29 connected to bus 220, or the negative terminal 30 con-I nected to the bus 210, The switch bar 28'is connected by shunt strap 31 with meter 32 and thence through automatic circuit breaker 33ftothe zone ieeder lead 27 The control of the entire series oftrolley wire zones, or of such portion thereofas may be fed from the station,-is thus readily effected by the station operatonf This is.,-not only of advantage during the operation of the system, since it enables the attendant to change the polarity ofthe trolley-wire of any section by [merely a l throwing the, switch 28; but it is alsoof great advantage when changing over an est ab-- lished system to the present layout, In the lattercase the switches 28 for the entire; panel may be connectedtemporarilyto one ot'the terminals 29 or 30, followed, when the installation is'otherwise in readiness, by theshift ing ofalternate switches to the terminal of oppositepolarityr I i I p The presentsystem has many advantages other than those mentioned above, such as dividing the load: properly between sources T ofpower supply; the elimination of all interference in other zones of the system when one zone is in trouble; the great reductionin temporary interruption of power supply; the reduction or elimination of return cables in'the track circuit; the elimination of concentrated current flow in the track circuit where many branch lines combine or converge; the elimination of extra heavy bonding; greatly reduced danger to per sons and objects on the breaking of trolley wires; the elimination of parallel cables to increasejthe conductivity ofjthe track circuit; the reduction of liability of damage to power generating apparatus; the reduction of trouble incident to lightning or insulation failures; an extensionlof thedis-i tance to which the system maybe carried economically from the source of power supply (oreinversely, the reduction in number of locations where the sourceof supplymust be available) the ease, and-economy; with;

whichthe various sources of supply may be, 1 a

interconnected "and the gen eral betterment;

as i 'tially at the same ,potential'and adapted to; serve a plurality of tracks,"a ground: connec tion for the several zones, a sour'ce, of'power,

of voltage conditions overthe entire system.

With the understanding that ourinvention be embodied in" various layouts I and equipment for obtaining the advantages stated, and further that l the accompanyii'ig drawings are but chagr'ammatic' indications of a la out merely illustrative of i the our invei'ition; We (3121 1111 thoughts which underlie whatweclaim as 1. In an electriclrailwaysystem ofthe C type, mutually insulated "trolley wire zones, mutually. connected tracks there-toga source orp'ower, separate means for connectmg each trolley wwire' zone to the source oi power, some of sa d zones being of oppos te pjolarity to other of said zones, whereby the current return is'mairrly through the ad oining zones and their'connection's to the source of power.-

' 2; An "lectric' railway, system including a pluralityof laterally adjacent tracks, asec:

tionalizedorzonedtrolley wire feeding each track, a source of power, and feeder connections'between said so'urce o' f-p'ower and each trolley wire 'zone, some'of SQ'I'Cl ZOIIBS lJGIIIg of opposite polarity toother ofthezones in the "same 1i1'1e',1the connections between "said zones and the source pewer bjei such that no'p'otentialdili erenceexists between thetrolley, wires for laterally adj acenttracks.

f 8. 1111 an electric railway system of the f-Dl C.-type,*m'utiially insulated trolley wire'zon'es, each zone comprising aplur lit of approxn mately parallel trolley wn-esjbeing substanmeans for separately eonnec't-ing each'zone to the source oi power, some of said zones being of opposite polar ty to other ofsaid zones,

. whereby theniain' returncurrent is carriedby nectionto the'ground connection designed to equalize the load'onthe severaltroll'eywire zones, means for separatelyconnecting each} thenegativo feeder and not by the ground connection except insofar as the returnrcurrent travels through ground to a nearby zone of opposite polarity, and meansfor altering at will the polarity of any zone of the'trol-r ley wire independently of all the other zones.

4, In an electric railway system of the D. C. type,- a source of power, mutually insulated trolley wire zones each connected to the source of power bya separatefeeder, a ground con-- nection for the several zones, a balancmg C011? nection to the. ground connection, some trolley .wire'z'ones being ofopposite polarity, where by the current return 1S 11l&1I1ly through. the adjoining zones and their COITDGClLlQIlSdlQillQ I source of power.

g 5. In an electric railway system of the D, type, mutually insulated trolleygwire zones;

a ground connection for the several zones, a source of powerincluding' a balancing con rate feeder whereby ,path is-througlr'thenegative feeder. :1

other feeders;

trolley wire zone to the sources ofpower, some i of said zones being ofopposite polarity to. V other of -SI1CLZO118S wherebyithemain current return is through the negative feeder, and

means foralteringaat will the polarityot' any. h zone of thetrolley wire independently of all theother izones'. I

6. Ina system of electrical distribution V a D. C. electric railway, a source of power,-v

: abalancing means including aneutral balanc-"= ing connection to the track in combination with a zoned line wherein each zone. is connected' by a separate lfeederxto the source of powenxf 7. Inasystem of electrical distribution for larity of any zone at will independently of all the other zones. vi

8min a :D. C. electric. railway systc1n,-'

source of power, a single; track, balancing means including a balancing connection to the-track, in combinationwith-mutually insulatedtrolley wire sectionsor zones for said i tracl n each of saidlsectio-ns or zones being connected tothe source of power by aceit 'the main return current 92111" an electricrailway system of theDf type, alzoned trolley line .each'zonephav- I ingra'sepalratezifeedenxa source oi D410. c.

power, distributing busses' connected to said" 1 source, feeder;} 'panels having switch means associated therewith, sa d switch means being adapted tov connect any feeder to either thepositive or negative bus,independently of the -10. In an electric railway system of the Dl (ltype, a zoned. t-rolley'li-ne each zone having a separate feeder, a source of-D. G; p0wer,'

distributing busses connected to said source,

feederv panels having switch means associated tlier'with,':sai ';l switch means being adapted I toeonnect any; feeder to either' thel 'positivei or negative bus, 'i-ndependentlyof the other feeders, in; combination "with balancing} means, and a common ground connection for nectedto-said ground connection.

the syste1n,,saidbalancing means being con p 11. ,In an electric railway'systenrof the D.

(l type, zoned -trolley line each zone havmg a separate feeder, asource'of D; C. power,

distributing 'hus'ses connected to saidsource, feeder panels having switch means associated therewith, i said switch means being adapted to connect anyfeedersflto either the positiveg or negative'bus,"independentlyof v the other feeders. and "ayground connection hav ng a balancing connection connected therewith. I L

Y ra -1mm electric railway system, a source 7 of power, positive and negative feeders connected thereto, mutually insulated trolley line zones, some of which are of opposite polarity to others, all the trolley wires in each zone. bein at substantially. the same potenv tial where y their insulation from the ground need be no greaterithan in a'single polarity V feedlng system in which the cars are run at the same potent-ial, and whereby no insulation is required between trolley wires within the zone. I

13. In an electric railway system, a source of power positive and negative feeders connected thereto, mutually insulated trolley line zones, some of which areof opposite po'larityio others, all the trolley wires in each a zone being at substantially the same potential whereby their insulation. from the ground need be no greater than in a single polarity V feeding system in which the cars are run at the same potential, and whereby no insulation is required betweentrolley wires within the I ing system to a double polarity feeding systern, comprising breaking the trolley line into a plurality of mutually insulated zones, connecting each zone through a separate feeder and a reversible switch means to the source 20f power, and, at the IIIOIDBIltf'fOI changing over, reversing some of said switch means whereby some zoneswill be of opposite polarity to others.

In testimony whereof we have signed our names to thisspecification.

. CHARLES eansrr.

CHARLES E. BENNETT. 

